Ah yes, that's it. Right now it's loking for /message-id/<looks like an email address>. I guess we need to expand that to also handle the /m/ links.
Should we do it for basically /(m|message-id/(xxxx), or do oyu think we need to actually limit it by the domain name as well? (We don't limit the postgresql.org one, but /message-id/ might be more unusual?)